Recently, various electronic devices such as a mobile phone, a mobile terminal, a personal computer, or the like, are provided with a display panel on which an optically transparent touch panel is attached. Such an electronic device can receive an instruction operation when a user operates on the surface of the touch panel with his/her finger, etc., while the user visually recognizes the display on the display panel through the touch panel.
As for such a touch panel, for example, an electrostatic capacitance touch panel is known, which has a transparent substrate on which a predetermined shaped transparent electrode pattern is formed in the X-direction, and similar transparent electrode pattern is formed in the Y-direction (the direction perpendicular to the X-direction).
A transparent electrode pattern used for the above-mentioned touch panel may have a problem which is usually referred to as “pattern visibility”, i.e., the electrode pattern is visible, due to the difference in optical property between a region where an electrode pattern is formed (conductive region) and a region where no electrode pattern is formed (non-conductive region). In order to prevent the “pattern visibility”, the gap between the boundaries of the transparent electrode patterns must be made extremely narrow. For example, in case of a electrostatic capacitance touch panel, the gap between the X-direction electrode pattern and the Y-direction electrode pattern must be 50 μm at the maximum, preferably 20 μm or less, more preferably 10 μm or less. Realizing such a narrow pitch is difficult by printing, and thus, such a pattern is made by photolithography.
For example, the Non-Patent Publication 1 mentioned below describes the following steps as an example of photolithography.
(1) A step for coating a conductive ink containing metal nanowires onto a substrate
(2) A step for curing to form a transparent conductive layer
(3) A step for forming a photosensitive resist on the transparent conductive layer
(4) A step for applying optical energy, through a light-shielding mask corresponding to a fine pattern, to the resist
(5) A step for developing a latent image of the obtained resist, by elusion using an appropriate developer
(6) A step for removing an exposed patterned film (transparent conductive layer) using an appropriate etching method
(7) A step for removing the remaining resist by an appropriate method
Further, Patent Publication 1 describes the following steps.
(1) A step for coating a conductive ink containing silver nanowires dispersed in water, onto a substrate
(2) A step for sintering to form a silver nanowire network layer.
(3) A step for forming a photo-curable matrix material containing a prepolymer, on the silver nanowire network layer
(4) A step for providing photon energy to the matrix material through an appropriate light-shielding mask corresponding to a fine pattern
(5) A step for removing a non-cured region by cleansing with a solvent (ethanol), or a step for physically removing the non-cured region using an adhesive tape or an adhesive roller